By default the HERO System leans towards "cinematic" resolution,
which is basically a euphemism for "Action Movie level of realism".
Dice rolls are weighted towards success (average roll of 11-
= 62.5%), rulings and ties favor the defender, points generally
round in a character's favor, and so forth. This is a very generous
and permissive approach and it works very well for many sorts
of campaigns.

This general bias exists in the realm of doing damage as well;
it's actually quite difficult to kill a character using
baseline stats, gear, and rules. Its much more likely a character
will be knocked out than killed when attacked.

If this suits your preference then the good news is you don't
have to change anything. This level of play is very forgiving,
Total Party Kills (TPK's) are practically unheard of, and
PC death will be a rare event. There is nothing intrinsically
wrong with this set up; in fact quite the opposite -- it works
great for certain styles of play and fits some genres perfectly,
including some sub-genres of Fantasy.

However most forms of Fantasy are generally more lethal than
this, with characters routinely slaying other characters, "monsters",
and what-have-you. In campaigns where this is the standard the
natural bias of the system presents several points of friction
that can detract from play. This ranges from combats taking
too long, large combats such as those common to some source
material impractical, and forcing characters to resort to "coup
de gras" vs. downed opponents to technically "kill"
them.

If the natural bias of the game towards non-lethal outcomes
isn't a good fit for your campaign, the good news is there
are literally a plethora of options for making things deadlier.
Presented here in the associated documents is a running list
of the options I consider to be most useful or deserving of
discussion. This list isn't comprehensive, but it should
cover enough ground to get you going.

However before entering into the discussion of how to make your
games more lethal, I will offer a little advice: don't go
hog-wild. Be careful and go slow; if adding options to an existing
campaign add them one at a time and try out the change before adding
another increased lethality option. You can always add more things over time,
but it is hard to take away options (particularly if one or more PC's have
been killed by a particular rule you instituted and now want to remove).

Along the same lines, if
starting up a new campaign choose options that suit the tone
you are going for but don't take more than one option you
aren't already personally familiar with from past usage.

Also always consider the personalities and tolerance for grit
of your players; many players will become unhappy if a campaign
gets too lethal / gritty even if they initially say that they
want it -- most players usually don't understand mechanics and game balance
well enough to really understand what they are
asking for when they say "more lethal", or more typically
really mean they want their characters to be more lethal
rather than the game itself to be more lethal.

In other words, often what players asking for more lethality really
want is for their PC's to kill their opponents faster, and they
generally don't really want their opponents to benefit from the same
advantages in a symmetrical, balanced model.